This invention relates to an improved rail mounting hole cap for closing a mounting bolt insertion hole (hereinafter referred to as "rail mounting hole") in a guide rail of a linear guide device.
In order to mount a guide rail of a linear guide device on a base of a machine by bolting, a plurality of rail mounting holes are formed through a guide rail of a linear guide device, and are spaced at equal intervals in an axial direction thereof. When a bolt is tightened, its head is received in the rail mounting hole, and is stepped downward from the upper surface of the rail, thereby forming a recess. Foreign matters tend to collect in this recess. Therefore, conventionally, the recess is closed by a cap so as to prevent foreign matters from collecting in the recess. There are known rail mounting hole caps of rubber or a synthetic resin having configurations as shown in FIGS. 9 and 10 and FIGS. 11 and 12. Such a rail mounting hole cap is attached by putting a flat metal member on the cap and then by driving the cap little by little using a hammer until the cap surface becomes flush with the upper surface of the rail.
However, each of the conventional rail mounting hole caps of the linear guide device is made of an elastic material such as rubber and a synthetic resin, and is fixed to the guide rail of metal, using its elasticity, and the cap is liable to be elastically deformed. And besides, a dimensional accuracy of the cap can not be easily achieved. Therefore, when the cap is excessively pressed during the attachment of the cap, there has been encountered a problem that the outer peripheral portion of the cap is deformed in shape, and is forced out of the rail mounting hole, or is withdrawn from the hole because of its loose fitting.
In order to prevent foreign matters from collecting, it is necessary that the upper surface of the rail and the cap surface be flat, and there has been encountered a problem that it is not easy to attach the conventional cap, made solely of a lowrigidity elastic material, in such a manner that the withdrawal of the cap is prevented and that the cap surface is flat.